A single‐center descriptive account of the use of pectoral nerve I and II nerve blocks for post‐operative pain relief following pediatric sternotomy

Abstract Regional anesthesia between the pectoralis major and minor was first described in 2011 as an alternative method to paravertebral blocks or epidurals for post‐operative mastectomies. Since then, the use of pectoral nerve (PECS) blocks for post‐operative pain management following thoracotomy, sternotomy, and other procedures in the anterior thorax has increased. While experience with this block is growing, the current understanding of its use in pediatric patients is limited. We reviewed pediatric cases at a single institution and provide a descriptive account of our use of PECS I and II blocks for post‐operative pain management following operations involving sternotomy in pediatric patients. We performed a retrospective database analysis of the use of PECS I and II blocks following procedures requiring sternotomy from 2018 to 2021 at St. Louis Children's Hospital. Patients 21 years old and younger who received either a PECS I or II block following a sternotomy for a cardiac procedure were included in the analysis. Patient's demographics, pre‐, intra‐, and post‐operative medications, operative time, extubation status, pain evaluations, and hospital course were assessed from the electronic medical record. From 2018 to 2021, 73 ultrasound‐guided PECS blocks were performed for pain relief for pediatric sternotomy. The most commonly performed operations were atrial septal defect closure (n = 12), mitral valve repair (n = 8), and ventricle septal defect closure (n = 8). Out of the 73 patients, 47 received a PECS I block and 26 received a PECS II Block. 70 of the blocks were administered after closure of the sternum while 3 were done before incision. The time to perform blocks took on average of 6 (±4) min. Mean operating room time was 7.5 h. Local anesthetics used for the blocks were as follows: Ropivacaine 0.2% (n = 54), Ropivacaine 0.5% (n = 18), and Bupivacaine 0.25% (n = 1). Twenty‐five out of 73 patients did not experience severe pain, defined as ≥7/10 on a numeric pain scale, at any point in the first 24 h following surgery. We describe the of use PECS I and II nerve block following pediatric sternotomy. Blocks were straight forward to perform, and typically took a short amount of time to administer (6 min), when compared to the total operating room time (7.5 h). While this study did not include a comparative group that did not receive a block, 34 percent of patients did not suffer from severe pain in the first 24 h following surgery. Further prospective studies are needed to assess the effectiveness of PECS blocks for pain relief following sternotomy in pediatric patients when compared to current standard of care. PECS blocks may be beneficial for a range of cardiac surgeries that typically result in severe postoperative pain.

. Twenty-five out of 73 patients did not experience severe pain, defined as ≥7/10 on a numeric pain scale, at any point in the first 24 h following surgery. We describe the of use PECS I and II nerve block following pediatric sternotomy. Blocks were straight forward to perform, and typically took a short amount of time to administer (6 min), when compared to the total operating room time (7.5 h). While this study did not include a comparative group that did not

| INTRODUC TI ON
The use of regional anesthesia for post-operative pain relief has become a staple in the hospital setting. These short procedures aim to decrease post-operative pain and the use of medications for pain relief. Regional anesthesia can occur throughout the body toward many nerves for a variety of procedures.
Fascial plane blocks between the pectoral muscles have been around for over 10 years and were originally described in 2011 by Blanco, who blocked the lateral and medial pectoral nerves during the perioperative period for breast surgeries. 1 Since then, the pectoral nerve (PECS) block nomenclature has evolved to be three different types: PECS I, PECS II, and serratus plane block. The PECS I block injects anesthetic in the interfacial plane between the pectoralis major and minor muscles at the 3rd rib, blocking the lateral and medial pectoralis nerves. The PECS II block, which was also developed by Blanco in 2012, is comprised of two injections: the PECS I injection with the addition of an injection in the interfacial plane between the pectoralis minor and serratus anterior muscles at the location of the 4th rib blocking the long thoracic nerve, thoracodorsal nerve, and intercostal nerves (T2-T6). 2 Lastly in 2013, Blanco described the serratus plane block around the serratus anterior muscle at the 5th rib blocking the intercostal nerves (T2-T6). 3 These blocks hope to decrease pain in the post-operative setting around the chest area for a variety of breast related procedures.
Traditionally, post-operative pain relief options include epidurals and paravertebral blocks at the levels of the operation, parasternal blocks, pecto-intercostal fascial blocks, transverse thoracic plane blocks, and erector spinae plane blocks. 4 The PECS block has been well established for its use in breast surgery for the adult population. [5][6][7] However, there has been a recent push in the last couple of years to find other uses for these types of blocks, especially in cardiac surgeries. 8 Despite its established efficacy in adults, the current understanding of its use in the pediatric population is limited.
The authors provide a descriptive study of the use of PECS I and PECS II blocks for pediatric sternotomy surgeries.

| ME THODS
This was a descriptive retrospective study that utilized the SlicerDicer tool within the Epic electronic medical record to identify patients who were under 21 years of age that were given a PECS I or II block following sternotomy for a cardiac procedure between January 1, 2018, and May 30, 2021, at St. Louis Children's Hospital.
SlicerDicer is a tool within EPIC to find specific patients based on specific inclusion and exclusion criteria that has been validated by previous studies. 9 The resulting patients were then assessed for demographics, pre-, intra-, and post-operative medications, operative time, extubation status, pain evaluations, and hospital course from the electronic medical record. As a result of variable time measurements using a combination of four different validated pain scales (rFLACC, FLACC, Faces, and Numeric) for each patient, a non-validated combination score was implemented to record pain levels. [10][11][12][13] Any post-operative outcomes and/or complications were recorded within 30 days following completion of the surgery. All patients received normal anesthetic nerve block post-operative care at St. Louis Children's Hospital consisting of pain service follow-ups, opioids, and non-opioid analgesics.

| RE SULTS
In total, 80 patients were obtained from the SlicerDicer search. After assessment of the patients, seven were removed as the blocks were not related to cardiac procedures. Therefore, 73 patients received PECS I or II blocks following sternotomy for cardiac procedures. Out of the 73 patients, 40 were male and 33 were female with an average age of 9 years and 99 days. Fifty-nine out of 73 patients were classified as American Society of Anesthesiologists (ASA) level 3. The most frequent surgery performed was closure of atrial septal defect at 12 operations and repair of mitral valve and ventricular septal defect at 8. Fifty-eight patients had a history of congenital heart disease as well. Demographics of the cohort is fully summarized in Table 1. Types of surgery's undergone by patients can be found in Figure 1, and the full list of surgeries can be found in Table S1. Five of the operations performed were due to the need of further procedures in the operating room, and eight of the patients had a previous sternotomy prior to the surgical course being evaluated.
Out of the 73 patients, 66 had same day surgery and seven were inpatients prior to surgery. The average length of stay following surgery in the intensive care unit (ICU) was 2.24 days for same day patients and 1.14 days for inpatients. The average length of stay in the hospital for non-ICU patients was 4.37 days for same day and 3.71 days for inpatient. The full hospital time course can be found in Table 2. The average length of time spent in the operating room receive a block, 34 percent of patients did not suffer from severe pain in the first 24 h following surgery. Further prospective studies are needed to assess the effectiveness of PECS blocks for pain relief following sternotomy in pediatric patients when compared to current standard of care. PECS blocks may be beneficial for a range of cardiac surgeries that typically result in severe postoperative pain.

K E Y W O R D S
Pain, PECS Block, Pediatrics, Sternotomy was 7 h and 28 min. Sixty-five patients received cardiopulmonary bypass during their operations with an average time of 2 h and 3 min.
Operating details of the patients can be found in Table 3.   In total, four patients arrived at the ICU still intubated and 69 arrived extubated. Every patient received some type of pain medication in the ICU with an average time of 91 min before administration.
The first pain medication given post-surgery, pain medications given in the first 24 h, and extubation status were recorded in Table 5.
In the ICU, nine patients reported nausea with five of those patients vomiting. There were no obvious adverse outcomes that we could directly attribute to the administration of the block in the ICU and zero patients were readmitted to the ICU after being admitted to the floor. Only one patient had an emergency room visit related to the surgery within 30 days post discharge.

| DISCUSS ION
Our data show that the use of PECS I and II blocks for post-operative An unexpected observation from these data was the increased time spent in the ICU and floor in the same day patients vs the inpatient patients. While outliers within these groups may be a reason for these numbers, the potential recovery time is interesting to note and should be understood by the physician performing the block.
A finding of these data is the need for clinicians and nurses to establish a consistent way to categorize pain. Pain scores in the Electronic Medical Record (EMR) were often recorded at variable time points, using multiple pain scores (rFLACC, FLACC, Faces, Numeric 1-10) within the same patient. There has been much education to our institution to improve this variance. Additionally, some patients had days where no pain score was recorded versus some patients that had a score being recorded every hour. Some patients had gone over 5 h initially in the ICU without a pain score observation. We recognize this may be because the patient is sedated but regardless, a system tracking and utilizing pain scores needs to be established. We also recognize the complexity of pain within the pediatric population and that individuals may not be able to verbally communicate with the care provider. That being said, the appropriate pain scale for varying cognitive levels and ages of patients' needs to be consistent among all providers. As a result of this inability to standardize the pain scores, we were forced to combine all pain scores regardless of measurement as a standard pain score. Despite this, it was found that 25 out of 73 patients did not experience severe pain,   Future studies are needed to assess the effectiveness of PECS blocks for pain relief following sternotomy in pediatric patients when compared to the current standard of care.
In conclusion, these findings show PECS I and II blocks for pediatric sternotomy as a promising technique for post-operative pain relief.
This study demonstrates the feasibility of the block but unfortunately showed significant variability in pain scores. Future prospective clinical trials should be utilized for the efficacy of this intervention within this population. Lastly, the need to standardize and categorize pain is of great importance to the medical community especially in the development of new techniques for pain management.

ACK N OWLED G M ENTS
This study was funded through the Medical Student Anesthesia

Research Fellowship through the Foundation for Anesthesia and
Research Summer Program.

This project was supported by a Medical Student Anesthesia
Research Fellowship (MSARF) from the Foundation for Anesthesia Education and Research (FAER) to ZF.

CO N FLI C T O F I NTE R E S T
The authors have nothing to disclose.